HOME and LImit switches

[wwolski]

Hi,
I am starting from scratch after upgrading my PC to the recommended NUC

I found information on programming the home and limit switches and this is not done yet
before I do I want to make to ensure that I put the homing switches mechanically in the correct places

Please see attached picture of the overhead of my homebuilt CNC router table and how I am referring to the axes

Some assumptions, please correct me if I'm wrong:
1. Home switches are all connected in series and are all normally closed using HomeAll
2. Home X switch opens when X reaches 0
3. Home Y switch opens when Y reaches 0
4. Home Z switch opens when Z reaches some position off the table eg 5 inches or so

Please explain what happens when I demand home, does the machine
move X (decreasing) until home all trips(switch opened), backs off until home all input is not tripped(switch closes)
then
move Y (decreasing) until home all trips(switch opened), backs off until home all input is not tripped(switch closes)

what happens with Z? Does it increase until the switch is opened?

Soft limits can be set for each axis to prevent the router exceeding X and X axis, not sure about the Z axis soft limit because bits can change
and touch off would set Z=0 at the top of the workpiece and workpiece thickness can also vary.

Thanks,
Wil

[wwolski]

Added missing diagram

[martyscncgarage]

You can put the home switches on either end of the axis. Its up to you. You can program their location in the Wizard in the Homing Section
Z+ is always at the top of its travel.

On a gantry type router, most guys want the router head away for loading material.

[ShawnM]

Hi Wil, I have my router setup to home to X0, Y0 as in your drawing. Z homes to the top. I then added a button on my VCP to "park" the spindle and the rear center of the table for loading/unloading material. My drawings are also drawn with X0, Y0 in the same position, lower left corner. I have soft limits only set for the max travel and they work perfectly.

[wwolski]

Hi

Maybe I misunderstand what homing is, I thought that this would bring the spindle to the origin so that one can zero the axes
It makes sense to home away from the x=y=0 position for loading
I want to be able to set the x and y to zero so without jogging there every time I power up the machine
I can do a touch off to zero the z, is this built into the CNC12 or does a macro need to be programmed as I had before?

Do people also do touch off with x and y axes? If so please point me to info

Also I didn't see a home all button on the control panel
I think the flow would be:

1. invoke home all - how?
2. load workpiece
3. set all axes to 0 using touch off
4. start milling

previously I ran a macro that did 3 and 4 when I started would prompt me to put the clip on the router bit etc
and then run, I would like to do that again so please point me to the current info on how to do this

Thanks
Wil

[ShawnM]

I think you are talking about two procedures. Auto homing the machine tells the Acorn where “machine” x0, y0 and z0 are located. Then it also knows its max travel from that point based on your soft limits. This way the Acorn knows your table work envelope is 4x9. This can be setup to run automatically all by itself. All you do is press cycle start after you power up the machine and it will run the auto homing macro that’s built into the software. Each axis moves one at a time towards your home switches, trips the switch, backs off the switch and sets “machine 0” for that axis. This has nothing to do with the workpiece x0, y0. Then you can load your workpiece and set your “part” x0, y0 and z0 and use a tool touch off if you like. This can also be done with a macro. Then you can start milling. Make sense?

You can manually set the machine zero coordinates, “invoke home all”, by manually jogging the spindle but I’m not sure why you’d wanna do this. I’m sure others will chime in and explain why some actually do this and their reasons why.

There is a button on the VCP labeled “reset home” and this will also run the auto homing macro.

[Gary Campbell]

Don't conflate a park location, often used to move the head to a location to facilitate loading with homing to machine coordinates.

The vast majority of router tables will home to the X and Y zero location in the lower left corner of the table. Z of course is up. These homing directions are set in the wizard and must match direction (+ & -) of switches set as limits

[martyscncgarage]

As others have said, you have MACHINE HOME position. It is the control's reference position for everything.
Then you have PART position which is an offset position from Machine Home.

You might take the time to read the Centroid Mill Operator's manual to give you the idea.
I am a mill/lathe guy. Router guys usually don't go to the detail.

You also might watch Centroid's mill training videos on YouTube just to give you the visual idea between homing the machine and setting part zero.
https://www.centroidcnc.com/centroid_di ... -v4.14.pdf